If someone makes a shidduch, the “minhag hamokem” is to pay before the wedding. It is not a choice if they want to or not, they owe the shadchon his/her wage. He/She worked hard on the shidduch (I would assume, most shidduchim are a huge headach) and even if it went easy that is norm in todays day and age.
Ofcourse, you did the right thing by asking about the payment. BTW what about his side, did they pay you? Good Luck! Hope it’s a big check at the end of all this.